1. Field of the Invention
This invention relates to a sewing apparatus including a sewing mechanism in which a thread cassette holding a needle thread is used and a control program therefor.
2. Description of the Related Art
U.S. Pat. No. 3,749,039 to Russell A. Fritts discloses a sewing apparatus with a cassette mount to which a thread cassette holding a needle thread wound on a thread spool is attached. In the disclosed sewing apparatus, a user pushes the thread cassette downward while holding the thread cassette in hand, in order that the thread cassette may be attached to the cassette mount of the sewing apparatus. Furthermore, when the thread cassette is to be ejected from the cassette mount, the user raises the thread cassette while holding the cassette in hand.
The above-described manual handling of the thread cassette imposes load on the user, and furthermore, force applied to the thread cassette differs in the magnitude from one user to another. Accordingly, each mechanism of the sewing apparatus is required to have a sufficient performance to cope with every condition. For example, the thread cassette is not always attached to the cassette mount under a constant condition. Accordingly, when threading is carried out upon attachment of the thread cassette, an operating condition of the threading mechanism needs to be determined so as to be reliably carried out in a wide range. As a result, the construction of the sewing apparatus is complicated.